Manufacture of thread



`mental oa. 1s, 1940 or, by mesne assignments, to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware Application February L7, 1934, Serialo. I711,751 14 claims. (c1. 1s`54 `This invention relates to themanufacture of thread. More particularly the invention relates tothe manufacture of thread of continuous rilarment character. Still more particularly the invention relates to an improved method of handling thread, such as regenerated cellulose rayon, regenerated cellulose horsehair and straw,

threads of other kinds such as of cellulose esters y and ethers, and particularly to threads of all kinds which may be processed in cake form and Whichexhibit a tendency to shrink during treatment.` The invention also relates to an improved spinning bucket. The invention will be described in its application to the particular field of regenerated cellulose thread as made by the viscose process, but it is to be understood that this particular description is not limitative of the invention. u E

In one method for the production of thread by the viscose process, a Viscose solution is forced through a spinnerette into a setting bath, through and from which it isfdrawn by a godet wheel and isfed into aswiftly revolving bucket whose essed either in the cake form, as spun, or after` rewinding into skeins. The processing of the thread involves treatment with various liquids'in order to remove the acid and soluble salts contained therein, and to desulphur, bleach, dye, or otherwise treat, to impart desirable characteristics to the finished product. Since the freshly formed thread is extremely tender and is easily damaged, i handling of the thread should be avoided as much as possible. It is therefore desirable to process the thread while wound in the form of a bucket-spun cake.

The thread shrinks in certain steps4 in processing and in drying. If the thread is freely suspended, this shrinkage may be 10% or more and is usually at least 5 However, when the bucket cake is subjected to purication treatment and drying, free-shrinkage of the yarn in parts `of the cake is prevented. For instance, when the yarn package is dried in the customary manner, the middle layers of the thread dry last and prevent free-shrinkage of the yarn comprising the outer layers of the cake. A thread, having varying denier, elongation, tenacity and especially varying shrinkage and dyeing properties, results. When this yarn is used in the manufacture of fabric, and is wetted and dried, the shrinkage Vis again variable "because part ofA the yarn has shrunk substantially its full amount and partis capable of additional shrinkage.

, With the` industry moving to higher and higher bucket speeds, and forming thicker and more compact cakes, it becomes increasingly difcult tocompletely and uniformly wash and purify the yarn in cake form. Various methods have been proposedl to softenthese thick, dense cakes, such ,as 'by flattening, elongating, et cetera, but, this is another costly step -in the process which can be avoided by practicing my invention, and which furthermore does not produce the uniform shrinkage characteristics obtained in the practice of' this invention.V

lIt is an object of this invention to prepare a bucket cake which can be quickly, uniformly, and thoroughly processed without unwinding, and to produceby bucket spinning a yarn having substantially uniform characteristics. Another object of the invention is to produce an apparatus capable of forming a bucket cake which may be treated as such without producing yarn of varying characteristics. Other objects of the invention will be in part apparent and in part set forth inthe following description.

u The objects of the invention are accomplished by spinning a bucket cake in which the circumference of an inner winding differs from the circumference of the adjacent outer winding by an amount `expressed by the formula: X =Y- (Z-l-V) Where X is the circumference of an inner winding, Y ,is the circumference of an outer winding, Z is the amount which an inner .winding in a truly circular bucket would differ from the adjacent outer winding, and V is an additional amount. The objects of the invention are accomplished, in the preferred embodiment of the invention, by

kthe use of a bucket having a sinuous inner Wall.

The objects of the invention are accomplished more particularly by spinning a bucket cake hav- ,ing a circumference, enlarged by axially alined `and Figure 6 is still another form of bar.

Referringnow to the numerals on the drawing, lli is` a bucket; l l are integral bar-like projections `on the interior of the `bucket placed approximately parallel to the axis of rotation and having a surface preferably, but not necessarily, in the invention.

Figure 4 shows a bar whose shape is preferred because it reduces looping of the thread to a minimum. Figures 5 and 6 show successful modiv ed bar shapes. V

In the form of the invention wherein an ordinary spinning bucket is modified to form an irregular cake, I prefer to use members of the shape shown in Figure 4. These members may be made of wood, rubber, Bakelite, casting aluminum, or some suitable alloy such as Woods metal, or of any other material which is capable of being formed to the desired shape and of resisting treating liquids. These members or bars are carefully fitted into position soas to preserve the balance of the bucket and to form a tight joint with the inner surface of the bucket. A suitable protective coating may be applied to the bucket interior to prevent damage to the yarn and infiltration of treating liquids beneath the bar. Examples of such coatings are rubber compositions, coating compositions resistant to the processliquids, layers ofresistant metals and the like.

A cake formed in my bucket follows the contour of the bucket until a reasonably large cake has been built up, after which the inside gradually takesthe form shown by the dotted line in Figure 1. By proper selection of the number, size, and shape of the sinuosities the shrinkage ofthe thread can be made substantially uniform throughout the cake.

The embodiments of my invention are capable of many modifications: The sinuosities can take the form of depressions in the side wall of the bucket rather than the form of raised members. The number, size, and location of the sinuosities or sinuosity-producing elements can be arranged to suit the needs of the particular process although, due to the high speeds at which the buckets revolve, best results will be secured by arranging the sinuosity-producing elements in balanced relation. The bars, or their equivalent in a molded bucket or liner, may be roughened to prevent the thread from slipping. Instead of using a molded bucket or of inserting bars in an ordinary bucket, a liner having an inner periphery constructed in accordance with the principles of this invention may be made, as by molding or casting, and iitted into the ordinary bucket. The size of the sinuosity-producing elements need not be the same and the sinuosity-producing elements need not be uniformly arranged so long as their arrangements meet the requirement of balance. The bars may be hollow when by the use of that construction a lighter weight will be advantageous. The bars or elements, due to the frustro conical shape of the usual bucket, are not precisely parallel to its axis of rotation. Furthermore, the bars may be placed at an angle'to a geometrical element of the bucket.

lThe invention has been described in its application to the spinning of rayon, but it is applicable to the spinning or winding of any thread and has `particular advantage where the thread is contractible.

`An .advantage of'my invention Ais in the production of thread of improved uniformity by the process involving treatment of the thread in cake form. Another advantage of my invention is in improving theV permeability of bucket cakes, whereby the quantity of materials and time required for treatment of the cakes are lessened. For instance, cakes have been spun under identical conditions from the same viscose solution according to standard methods and in accordance with this invention, respectively, and where the standard cake required upward of twentyfive hours for washing free of acid, the cake spun according to my 'invention was washed free of acid in six hours. Another advantage of the iny vention is in substantially overcoming undesirable shrinkage effects during the several steps of cake treatment and in the production of yarn which is approximately physically uniform without resort to the skein process. By this invention an easily processed cake is produced even at bucket speeds which produce by prior art processes cakes too impermeable to treat successfully in cake form. Other advantages of the invention will be apparent.

My invention has been described most particularly in its application to the bucket spinning of thread, and it is in this operation that the invention exhibits its greatest advantages. It is to be understood, however, that the novel centrifugal bucket to which the invention pertains is also applicable to the centrifugal washing and/or the centrifugal wringing or drying 0f bucket cakes. Thus, after spinning in a bucket of the type described for use in my invention, buckets embodying the same principle of operation or of the same or similar design can be used for the centrifugal washing or other wet-processing or drying (wringing) operations to which the thread may be subjected. Similarly, bucket cakes which have been formed in the ordinary bucket can subsequently be centrifugally washed or wetprocessed or dried in centrifugal buckets made in accordance with the principles of this invention, compensating shrinkage taking place to a certain extent, even where the thread has been spun without the use of the novel centrifugal bucket. It is preferable to use a bucket of slightly smaller diameter for processing cakes than is used in the spinning thereof, since there is some contraction of the cake immediately after its formation. It is also advantageous to centrifugally wring or whiz the cakes prior to drying at high speeds, such as, for instance, at 6,000, or even as much as 8,000 R. P. M. or more, in order to remove as much liquid as is possible before drying with warm air, and thereby retard the forcing of the impurities to the surface of the thread during drying. i

As many apparently widely different embodiments of this invention may be made without departing from the spirit and scope thereof, it is to be `understood that I do not limit myself to the specic embodiments thereof except as defined in the appended claims.

The apparatus and cake described herein form the subject matter of my copending application, Serial No. 628,317, filed August 11, 1932.

' I claim:

1. In the method of treating artificial thread bucket cakes for wet-processing, drying, and the like, the steps which comprise imparting to a bucket cake an irregular outer circumference to impart slack throughout all parts of the cake wherein Iresistance to contraction would otherwise occur when the cake is dried, then subjectlike, the steps which comprise imparting to` a bucket cake a sinuous outer circumferencel to impart slack throughout all parts of the cake wherein resistance to contraction would otherwise occur when the cake is dried, then subjecting the cake to centrifugal action `while maintaining said sinuous outer circumference of thev cake.

3. A process which comprises subjecting a cake of artificial thread having a sinuous outer circumference sufficient to impart slack throughout all parts of the cake wherein resistance to contraction would otherwise occur when the cake is dried, to liquid treatments While substantially maintaining said sinuous circumference of `said cake.

4. A process which comprises producing a cake of artificial thread having slack throughout all parts thereof wherein resistance to contraction would otherwise occur when the cake is dried, disposing said cake in a holder having an inner wall complemental to the shape of said cake, and wet-processing said cake while in said holder.

5. A process which comprises producing a cake of artificial thread having slack throughout all parts thereof wherein resistance to contraction would otherwise occur when the cake is dried, disposing said cake in a holder having an inner wall complemental to the shape of said cake, wetprocessing said cake `while in said holder, and whizzing said cake while in said holder.

6. A process which comprises producing a cake of `artificial thread having slack throughout all parts thereof wherein resistance to contraction would otherwise occur when the cake is dried, disposing said cake in a holder having an inner wall complemental tothe shape of said cake, and centrifugally washing said cake while in said holder.

7. A process which comprises wet-processing a cake of artificial thread having slack throughout all parts thereof wherein resistance to contraction would otherwise occur when the cake is dried while substantially maintaining the shape of said cake, and subsequently drying said cake.

8. A process which comprises whizzing a cake of articial'thread having slack throughout all parts thereof wherein resistance to contraction would otherwise occur when the cake is dried while substantially maintaining the shape of said cake, and subsequently drying said cake.

9. A process which comprises spinning a cake of artificial thread in a bucket having an inner surface provided with inwardly projecting portions of such conformations as to produce a corrugated, endless, inner wall, the saidv corrugations being of sunicient size and shape to introduce slack throughout all parts of the thread package wherein resistance to contraction would otherwise occur when the package is formed and dried, removing said cake from said bucket, disposing said cake ina holder having aninner wall complemental to the shape of said cake, wetprocessing and whizzingA said cake While in said holder. o

10. A process which comprises spinning a cake of articial thread in a bucket having an inner surface provided with inwardly projecting pory tions of such conformations as to produce a corrugated, endless, inner wall, the said corrugations being of suflicient size and shape to introduce slack throughout all parts of the thread package wherein resistance to contraction would otherwise occur when the package is formed and dried, removing said cake from said bucket, disposing said cake in a holder having an inner wall complemental to the shape of said cake, and centrifugally washing said cake in said holder.

ll. A process which comprises spinning a cake of artificial thread in a bucket having an inner surface provided with inwardly projecting portions of such conformations as to produce` a corrugated, endless, inner wall, the said corrugations being of sufficient size and shape to introduce slack throughout all parts of the thread package wherein resistance to contraction would otherwise occur when the package is formed and dried, removing said cake from said bucket, disposing said cake in a holder having an inner wall complemental to the shape of said cake, said holder having a diameter slightly smaller than the diameter of said bucket, and wet-processing said cake in said holder.

12. A process which comprises spinning a cake of articial thread in a bucket having an inner surface lprovided with inwardly projecting portions of such conformations as toproduce a corrugated, endless, inner wall, the said corrugations being of sufficient size and vshape to introduce slack throughout all parts of the thread package wherein resistance to contraction would otherwise occur when the package is formed and dried, removing said cake from said bucket, disposing said cake in a holder having an inner wall complemental to the shape of said cake, said holder` having a diameter slightly smaller than the diameter of said bucket, centrifugally whizzing said cake and holder at a high speed, and thereafter drying said cake.

13. In the manufacture of rayon, the process of makingrayon yarn having increased uniformity of dyeing quality which comprises forming a rayon yarn cake having a predetermined roughly clover-leaf shape, with alternating interior and exterior corrugations in its walls, and adapted to promote uniform shrinkage and tension of the yarn throughout the cake during processing thereof, then liquid processing the cake by forcing the treating liquid from the interior of the cake outwardly therethrough while positively maintaining the cake in substantially the` same shape and form by supporting the cake at its outer surface, partially drying the cake centrifugally by rapid rotation of the cakev about its own axis, while supporting the cake over substantially the whole of its exterior surface, and thereafter further drying the cake while the same is free to shrink at its indented portions.

14. In a process for manufacturing rayon by the centrifugal spinning method, the steps which comprise treating a clover-leaf-shaped yarn cake with a desired processing liquid by forcing the liquid through the cake from the interior outwardly while the cake is maintained in roughly clover-leaf form during liquid treatment and is positively supported at its exterior surface, and thereafter drying the cake while so supporting the same as to permit shrinkage of the yarn therein.

l SEYMOUR W. BRAINARD. 

